From what it looks like... I can't really imagine it. Many of the minions you'd resurrect are not very impactful against Big Priest (Tar Creeper, Unstable Ghoul, Explosive Sheep, Abomination), Big Priest has means to handle standalone threats like the Lich King, and should you have the iniative on the board, Psychic Scream will punish you hard. Sylvanas might be able to turn the game around, but it's difficult for me to imagine it would win the game on the spot.
But maybe I'm wrong. Against most of the aggressive decks, however, I can imagine it would do fairly well, as Taunt Druid always has.
You'd be surprised at the cumulative effect of multiple explosive minions being re-summoned over and over. Big Priest is not it's best matchup, but I've beaten plenty of them. Sylvanas and Umbra are out, I'll update the decklist again since it didn't save apparently.